Chemical vapor deposition growth of boron-carbon-nitrogen layers from methylamine borane thermolysis products.

This work investigates the growth of B-C-N layers by chemical vapor deposition using methylamine borane (MeAB) as the single-source precursor. MeAB has been synthesized and characterized, paying particular attention to the analysis of its thermolysis products, which are the gaseous precursors for B-C-N growth. Samples have been grown on Cu foils and transferred onto different substrates for their morphological, structural, chemical, electronic and optical characterizations. The results of these characterizations indicate a segregation of h-BN and graphene-like (Gr) domains. However, there is an important presence of B and N interactions with C at the Gr borders, and of C interacting at the h-BN-edges, respectively, in the obtained nano-layers. In particular, there is a significant presence of C-N bonds, at Gr/h-BN borders and in the form of N doping of Gr domains. The overall B:C:N contents in the layers is close to 1:3:1.5. A careful analysis of the optical bandgap determination of the obtained B-C-N layers is presented, discussed and compared with previous seminal works with samples of similar composition.

Chlorine Insertion Promoting Iron Reduction in Ba-Fe Hexagonal Perovskites: Effect on the Structural and Magnetic Properties.

BaFeCl0.13(2)O2.48(2) has been synthesized and studied. A proper tuning of the synthetic route has been designed to stabilize this compound as a single phase. The thermal stability and evolution, along with the magnetic and structural properties are reported here. The crystal structure has been refined from neutron powder diffraction data, and it is of the type (hhchc)2-10H. It is stable up to a temperature of 900 °C, where the composition reads BaFeCl0.13(2)O2.34(2). The study by electron microscopy shows that the crystal structure suffers no changes in the whole BaFeCl0.13(1)O3-y (2.34 ≤ 3 - y ≤ 2.48) compositional range. Refinement of the magnetic structure shows that the Fe is antiferromagneticaly ordered, with the magnetic moment parallel to the ab plane of the hexagonal structure. At higher temperature, a nonreversible phase transition into a (hchc)-4H structure type takes place with overall composition BaFeCl0.13(1)O2.26(1). Microstructural characterization shows that, in some crystals, this phase intergrows with a seemingly cubic related phase. Differences between these two crystalline phases reside in the chlorine content, which keeps constant through the phase transition for the former and disappears for the latter.

Protecting TiS3 Photoanodes for Water Splitting in Alkaline Media by TiO2 Coatings.

Titanium trisulfide (TiS3) nanoribbons, when coated with titanium dioxide (TiO2), can be used for water splitting in the KOH electrolyte. TiO2 shells can be prepared through thermal annealing to regulate the response of TiS3/TiO2 heterostructures by controlling the oxidation time and growth atmosphere. The thickness and structure of the TiO2 layers significantly influence the photoelectrocatalytic properties of the TiS3/TiO2 photoanodes, with amorphous layers showing better performance than crystalline ones. The oxide layers should be thin enough to transfer photogenerated charge through the electrode-electrolyte interface while protecting TiS3 from KOH corrosion. Finally, the performance of TiS3/TiO2 heterostructures has been improved by coating them with various electrocatalysts, NiSx being the most effective. This research presents new opportunities to create efficient semiconductor heterostructures to be used as photoanodes in corrosive alkaline aqueous solutions.

Insights into Palladium Deactivation during Advanced Oxidation Processes.

A key step in creating efficient and long-lasting catalysts is understanding their deactivation mechanism(s). On this basis, the behavior of a series of Pd/corundum materials during several hydrogen adsorption/desorption cycles was studied using temperature-programmed desorption coupled with mass spectrometry and aberration-corrected transmission electron microscopy. The materials, prepared by impregnation and by sputtering, presented uniform well-dispersed Pd nanoparticles. In addition, single atoms and small clusters of Pd were only detected in the materials prepared by impregnation. Upon exposure to hydrogen, the Pd nanoparticles smaller than 2 nm and the single atoms did not present any change, while the larger ones presented a core-shell morphology, where the core was Pd and the shell was PdH x . The results suggest that the long-term activity of the materials prepared by impregnation can be attributed solely to the presence of small clusters and single atoms of Pd.

Perylene-labeled silica nanoparticles: synthesis and characterization of three novel silica nanoparticle species for live-cell imaging.

The increasing exposure of humans to nanoscaled particles requires well-defined systems that enable the investigation of the toxicity of nanoparticles on the cellular level. To facilitate this, surface-labeled silica nanoparticles, nanoparticles with a labeled core and a silica shell, and a labeled nanoparticle network-all designed for live-cell imaging-are synthesized. The nanoparticles are functionalized with perylene derivatives. For this purpose, two different perylene species containing one or two reactive silica functionalities are prepared. The nanoparticles are studied by transmission electron microscopy, widefield and confocal fluorescence microscopy, as well as by fluorescence spectroscopy in combination with fluorescence anisotropy, in order to characterize the size and morphology of the nanoparticles and to prove the success and homogeneity of the labeling. Using spinning-disc confocal measurements, silica nanoparticles are demonstrated to be taken up by HeLa cells, and they are clearly detectable inside the cytoplasm of the cells.

Economic evaluations of implantable cardioverter defibrillators: a systematic review.

The aim of this paper was to review the cost-effectiveness studies of implantable cardioverter defibrillators (ICD) for primary or secondary prevention of sudden cardiac death (SCD). A systematic review of the literature published in English or Spanish was performed by electronically searching MEDLINE and MEDLINE in process, EMBASE, NHS-EED, and EconLit. Some keywords were implantable cardioverter defibrillator, heart failure, heart arrest, myocardial infarction, arrhythmias, syncope, sudden death. Selection criteria were the following: (1) full economic evaluations published after 1995, model-based studies or alongside clinical trials (2) that explored the cost-effectiveness of ICD with or without associated treatment compared with placebo or best medical treatment, (3) in adult patients for primary or secondary prevention of SCD because of ventricular arrhythmias. Studies that fulfilled these criteria were reviewed and data were extracted by two reviewers. The methodological quality of the studies was assessed and a narrative synthesis was prepared. In total, 24 studies were included: seven studies on secondary prevention and 18 studies on primary prevention. Seven studies were performed in Europe. For secondary prevention, the results showed that the ICD is considered cost-effective in patients with more risk. For primary prevention, the cost-effectiveness of ICD has been widely studied, but uncertainty about its cost-effectiveness remains. The cost-effectiveness ratios vary between studies depending on the patient characteristics, methodology, perspective, and national settings. Among the European studies, the conclusions are varied, where the ICD is considered cost-effective or not dependent on the study.

Rapid degradation of zinc oxide nanoparticles by phosphate ions.

Zinc oxide nanoparticles are highly sensitive towards phosphate ions even at pH 7. Buffer solutions and cell culture media containing phosphate ions are able to destroy ZnO nanoparticles within a time span from less than one hour to one day. The driving force of the reaction is the formation of zinc phosphate of very low solubility. The morphology of the zinc oxide particles has only a minor influence on the kinetics of this reaction. Surface properties related to different production methods and the presence and absence of labelling with a perylene fluorescent dye are more important. Particles prepared under acidic conditions are more resistant than those obtained in basic or neutral reaction medium. Surprisingly, the presence of a SiO2 coating does not impede the degradation of the ZnO core. In contrast to phosphate ions, ß-glycerophosphate does not damage the ZnO nanoparticles. These findings should be taken into account when assessing the biological effects or the toxicology of zinc oxide nanoparticles.